Of course it should be possible to change D/T values if necessary.
(As well as owner, type, attributes, etc.)
But I (and all other cachers that I know) don't want that the changed values affect our official statistics of our founds.
Of course I can track the statistics by myself. I've written a program for that (similar to GSAK).
But the produced statistics are not the official GC statistics and therefore not accepted for challenges.
In my opinion it should be easy possible to store the current D/T values (and maybe other values like type, coordinates, or owners name) together with the log entry when logging the cache. The statistics build process should be then generate faster results because it doesn't has to lookup cache data for each found.
Storing the D/T history at a cache (maybe created by an special log type) would be more precise, but would otherwise produce more lookups.